Glycoproteins and glycolipids are ubiquitous components of animal cell membranes. They possess a wide variety of different properties and may function as enzymes, structural membrane molecules and specific receptors at the cell surface. In addition, certain glycoproteins are secreted into the extracellular environment. In many instances, evidence has been obtained that the carbohydrate moieties associated with glycoproteins and glycolipids play a central role in their respective biological function. However, detailed descriptions of specific roles at the molecular level have been obtained in only a few cases. Thus one of the major challenges facing cell biologists is the molecular definition of the biological roles of carbohydrate. This challenge provides a focus for the Gordon Conference on Glycoproteins and Glycolipids to be held in August, 1981, at the Kimball Union Academy. Definition of the biological roles of carbohydrate at the molecular level requires a broad interdisciplinary approach. The Conference will begin with two sessions devoted to recent developments in carbohydrate structural analysis and to a summary of new structures identified by these techniques. The next two sessions will survey normal mechanisms of biosynthesis of glycoproteins, and mutations in glycosylation. Single sessions will be devoted to the emerging biological roles of proteoglycans in cellular differentiation and adhesion; to the roles of carbohydrates in receptor recognition, such as clearance of glycoproteins from the circulation and uptake of lysosomal enzymes by fibroblasts; and to interactions of carbohydrates with antibodies and lectins. The final two sessions will be devoted to biological roles of carbohydrate in cellular interactions in the developing embryo, the developing slime mold, and in the mating of yeast.